"I'm not in love with propane on a boat,
primarily for safety reasons, but also because it's a pain to swap out
the tanks, leak check, etc. Don't forget to leak check with soapy
water, very important."

In all the years I've been running GBs, I've never seen a problem with the propane setup on one. And while I agree it doesn't hurt to check for leaks at swap out, it's no big deal to do and one bottle alone should last you for several months.

As I recall all the GBs I've been involved with, including my own, have had horizontal bottles and I've never seen a problem with that setup.